Remove static sitemap, generate 'dynamic' sitemap

[kevinmitch14]

Current sitemap.xml has static <lastmod>2023-04-06</lastmod>. This will have to be changed manually or will always stay as the same outdated value.

Replaced it with a generated Sitemap (see NextJS docs).

Old output:

<?xml version="1.0" encoding="UTF-8"?>
<urlset xmlns="http://www.sitemaps.org/schemas/sitemap/0.9">
  <url>
    <loc>https://marker.ping.gg</loc>
    <lastmod>2023-04-06</lastmod>
  </url>
</urlset>

New output:

<urlset xmlns="http://www.sitemaps.org/schemas/sitemap/0.9">
  <url>
    <loc>https://marker.ping.gg</loc>
    <lastmod>2023-04-06T15:02:24.021Z</lastmod>
  </url>
</urlset>

However, <lastmod/> will always be up to date with new approach, because it is using new Date() on build.

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Name	Status	Preview	Comments	Updated (UTC)
markerthing	✅ Ready (Inspect)	Visit Preview	💬 Add feedback	Apr 15, 2023 11:21pm